Engine Control System - 3.8L - DTC P0220 to DTC P0449 Buick LaCrosse I

Circuit Description

The throttle body assembly contains the following components

1. The throttle blade
2. The throttle actuator motor
3. The throttle position (TP) sensor 1 and 2
4. The throttle actuator control (TAC) module

The TAC system monitors the throttle position with 2 sensors. If the powertrain control module (PCM) receives a message from the TAC module that indicates TP sensor 2 voltage is outside a predetermined range, DTC P0220 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P0220 Throttle Position (TP) Sensor 2 Circuit

Conditions for Running the DTC

1. DTCs P0606, P1518 and P2108 are not set.
2. The ignition switch is in the crank or the run position.
3. The ignition voltage is more than 5.23 volts.
4. The communications between the TAC module and the PCM must be valid.

Conditions for Setting the DTC

1. The TP sensor 2 voltage is less than 0.282 volts or more than 4.6 volts.
2. The PCM learns a minimum throttle position of more than 0.813 volts.
3. The TP sensor reference voltage is less than 0.5 volt.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0220

The powertrain control module (PCM) provides ignition positive voltage to the coil side of the fuel pump relay. When the ignition switch is first turned ON, the PCM energizes the fuel pump relay, which applies power to the fuel pump. The PCM enables the fuel pump relay as long as the engine is cranking or running and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the PCM de-energizes the fuel pump relay after 2 seconds. The PCM monitors the voltage on the fuel pump relay control circuit. If the PCM detects an incorrect voltage on the fuel pump relay control circuit, DTC P0230 sets.

This diagnostic procedure supports the following DTC

DTC P0230 Fuel Pump Relay Control Circuit

1. The ignition is ON.
2. The system voltage is between 9-18 volts.

1. The PCM detects an incorrect voltage on the control circuit of the fuel pump relay.
2. The condition exists for less than 1 second.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2: Listen for a click when the fuel pump relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4: This step verifies that the PCM is providing voltage to the fuel pump relay.
3. 5: This step tests for an open in the ground circuit to the fuel pump relay.
4. 6: This step tests if voltage is constantly being applied to the control circuit of the fuel pump relay.

DTC P0230

System Description

The powertrain control module (PCM) uses information from the ignition control module (ICM) and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

1. DTC P0101, P0102, P0103, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, if applicable, P0128, P0315, P0335, P0336, P0340, P0341, P0350, P0502, P0503, P1350 are not set.
2. The engine speed is between 475-5,850 RPM.
3. The ignition voltage is between 9-18 volts.
4. The engine coolant temperature (ECT) is between -7 and +125°C (+21 and +257°F).
5. The fuel level is more than 10 percent.
6. The Antilock Brake System (ABS) and the Traction Control System are not active.
7. The transmission is not changing gears.
8. The A/C clutch is not changing states.
9. The PCM is not in fuel shut-off or decel fuel cut-off mode.
10. The PCM is not receiving a rough road signal.

The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

1. The control module flashes the MIL if the misfire will damage the catalyst.
2. The control module illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails.
3. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

1. Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration: Variable thickness brake rotors-Refer to «Symptoms - Hydraulic Brakes»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__symptoms-hydraulic-brakes) . Worn or damaged accessory drive belt-Refer to «Symptoms - Engine Mechanical»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) .
2. Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

The number below refers to the step number on the diagnostic table.

1. 2: If the actual CKP variation values are not within the learned values, the misfire counters may increment.

DTC P0300

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft and the crankshaft position sensor. The calculated error allows the powertrain control module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.

The CKP system variation compensating values are stored in PCM memory after a learn procedure has been preformed. If the actual CKP variation is not within the CKP system variation compensating valves stored in the PCM, DTC P0300 may set. If the CKP system variation values are not stored in the PCM memory, DTC P0315 sets.

This diagnostic procedure supports the following DTC

DTC P0315 Crankshaft Position (CKP) System Variation Not Learned

This diagnostic runs continuously.

The CKP system variation values are not stored in the PCM memory for more than 0.5 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0315

Diagnostic Fault Information

DTC P0325, P0326, P0327 or P0332

Typical Scan Tool Data

Spark

Circuit/System Description

The Knock Sensor (KS) System enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors are located below each cylinder head on the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The control module adjusts the spark timing based on the amplitude and the frequency of the KS signal. The control module receives the KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit. The control module learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The control module should monitor a normal KS signal within the noise channel. If the control module malfunctions in a manner that will not allow proper diagnosis of the KS system, DTC P0325 sets. If the control module detects the KS signal outside of the noise channel or the KS signal is not present. DTC P0327 refers to the bank 1 KS and DTC P0332 refers to the bank 2 KS.

1. DTC P0016, P0101, P0102, P0103, P0116, P0117, P0118, P0120, P0125-L32 only, P0128, P0220, P0335, P0336, P0340, P0341, P0608, P1125, P1516, P2101, P2108, P2120, P2125, P2135 or P2138 is not set.
2. The engine speed is between 1,000-5,000 RPM.
3. The throttle position (TP) indicated angle is more than 10 percent.
4. The engine load is more than 40 percent.
5. The engine coolant temperature (ECT) is more than 60°C (140°F).
6. The knock retard is less than 15 degrees.
7. The ignition 1 signal is more than 9 volts.
8. The engine run time is more than 30 seconds.
9. DTC P0325, P0327 and P0332 run continuously once the above conditions are met.

P0325

The control module detects a malfunction in the KS diagnostic circuitry that will not allow proper diagnosis of the KS system.

P0327 or P0332

The KS signal is outside of the assigned noise channel or the KS signal is not present for more than 0.5 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect the KS for physical damage. A KS that is dropped or damaged may cause a DTC to set.
2. Inspect the KS for proper installation. A KS that is loose or over torqued may cause a DTC to set. The KS should be free of thread sealant. The KS mounting surface should be free of burrs, casting flash and foreign material.
3. The KS must be clear of hoses, brackets and engine electrical wiring.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Circuit/System Testing

1. Test for an intermittent and for a poor connection at the affected KS.
2. With the ignition OFF, disconnect the affected KS.
3. With the ignition OFF, measure the resistance for infinite ohms from the sensor signal terminal on the KS to a good ground and the low reference terminal on the KS to a good ground with a DMM. If resistance does not measure infinite ohms at both terminals, then replace the affected KS.
4. Connect the DMM between the terminals of the affected KS. Set the DMM to the 400 Hz scale, let stabilize at 0 Hz. Tap on engine block with a non-metallic object near the affected KS while observing the signal indicated on the DMM. If the DMM does not display a fluctuating frequency while tapping on the engine block then replace the affected KS.
5. Turn the ignition ON, engine OFF. Set the DMM to the DC voltage scale. Measure for 4.2 volts from the KS signal circuit to a good ground and the KS low reference circuit to a good ground with the DMM. If over 4.2 volts with the ignition OFF, disconnect the control module and test the KS signal circuit or the KS low reference circuit for a short to voltage. If under 4.2 volts with the ignition OFF, disconnect the control module test the KS signal circuit or the KS low reference circuit for an open, short to ground or high resistance.
6. Test for intermittent or poor connections at the control module.
7. If all circuits test normal, then replace the control module.

Repair Procedures

1. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for ECM replacement, setup and programming
2. «Knock Sensor (KS) 1 Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
3. «Knock Sensor (KS) 2 Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The crankshaft position (CKP) sensor contains 2 hall-effect switches in one housing. This sensor configuration produces 2 separate CKP sensor pulses. These pulses occur when 2 interrupter rings, mounted to the crankshaft balancer, the outer one containing 18 evenly spaced windows and blades, the inner one containing 3 unevenly spaced windows and blades, pass by the sensors. The 18X sensor produces 18 pulses per engine revolution. The 3X sync sensor produces 3 pulses per engine revolution, each pulse representing a pair of companion cylinders. Both sensors are connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits

1. The CKP sensor 1 signal circuit
2. The CKP sensor 2 signal circuit
3. A shared 12-volt reference circuit
4. A shared low reference circuit

The ICM uses the sensors to determine the engine position and speed. A signal converter within the ICM, using the CKP sensor 1 18X pulse, produces a digital 18X output signal to the powertrain control module (PCM) on the medium resolution engine speed signal circuit. The PCM monitors the medium resolution engine speed signal circuit for errors. If the PCM does not receive a signal from the ICM, DTC P0335 sets.

This diagnostic procedure supports the following DTC

DTC P0335 Crankshaft Position (CKP) Sensor A Circuit

1. The engine run time is more than 3 seconds.
2. This diagnostic runs continuously when the above condition is met.

1. The PCM detects the following for every 2 engine revolutions: 6 low resolution engine speed signals 1 camshaft position (CMP) sensor signal 0 medium resolution engine speed signals
2. The above conditions are met for more than 8 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0335

The crankshaft position (CKP) sensor contains 2 hall-effect switches in one housing. This sensor configuration produces 2 separate CKP sensor pulses. These pulses occur when 2 interrupter rings, mounted to the crankshaft balancer, the outer one containing 18 evenly spaced windows and blades, the inner one containing 3 unevenly spaced windows and blades, pass by the sensors. The 18X sensor produces 18 pulses per engine revolution. The 3X sync sensor produces 3 pulses per engine revolution, each pulse representing a pair of companion cylinders. Both sensors are connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits

1. The CKP sensor 1 signal circuit
2. The CKP sensor 2 signal circuit
3. A shared 12-volt reference circuit
4. A shared low reference circuit

The ICM uses the sensors to determine the engine position and speed. A signal converter within the ICM, using the CKP sensor 1 18X pulse, produces a digital 18X output signal to the powertrain control module (PCM) on the medium resolution engine speed signal circuit. The PCM monitors the medium resolution engine speed signal circuit for errors. If the PCM receives an incorrect number of signals from the ICM, DTC P0336 sets.

This diagnostic procedure supports the following DTC

DTC P0336 Crankshaft Position (CKP) Sensor A Performance

1. The engine run time is more than 3 seconds.
2. This diagnostic runs continuously when the above condition is met.

1. The PCM detects the following for every 2 engine revolutions: 6 low resolution engine speed signals 1 camshaft position (CMP) sensor signal A number other than 0 or 36 medium resolution engine speed signals
2. The above conditions are met for more than 8 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0336

The camshaft position (CMP) sensor is a 1X sensor. The CMP provides one digital ON/OFF signal to the powertrain control module (PCM) per revolution of the camshaft. This information is used by the PCM to determine the position of the valve train relative to the crankshaft position (CKP). By monitoring the CMP and CKP signals, the PCM can accurately time the operation of the fuel injectors. The CMP sensor is connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits which are shared with the CKP sensor

1. The CMP sensor signal circuit
2. A 12-volt reference circuit
3. A low reference circuit

The signal is passed through the ICM to the PCM on the camshaft position signal circuit. The PCM monitors the CMP sensor for errors. If the PCM does not receive a signal from the CMP sensor, DTC P0340 sets.

This diagnostic procedure supports the following DTC

DTC P0340 Camshaft Position (CMP) Sensor Circuit

1. The engine is cranking. OR
2. The engine is running for more than 3 seconds.
3. This diagnostic runs continuously when either condition is met.

1. The PCM detects the following for every 2 engine revolutions: 36 medium resolution engine speed signals 6 low resolution engine speed signals 0 camshaft position signals
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Inspect for the following conditions

1. Any secondary ignition wires arcing to a wiring harness and for carbon tracking or other signs of damage
2. A faulty ignition coil
3. The ignition control module and the coils for cracks, carbon tracking or other signs that indicate that the coil secondary circuit is arcing to the ICM or to the ICM wiring harness. Refer to «Ignition Coil(s) Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

If the condition is suspected of being intermittent, refer to Testing for Intermittent Conditions and Poor Connections .

The numbers below refer to the step numbers on the diagnostic table.

1. 14: This test verifies if the sensor is working correctly. By suppling a ground to the circuit, the voltage should change when the circuit is touched with a test lamp.
2. 26: This step determines if the fault is caused by a missing camshaft magnet or by a faulty PCM. The voltage measured in this step should be near 5 volts and decrease to near 0 volts when the CMP sensor interfaces with the camshaft magnet.

DTC P0340

The camshaft position (CMP) sensor is a 1X sensor. It provides 1 digital ON/OFF signal to the powertrain control module (PCM) per revolution of the camshaft. This information is used by the PCM to determine the position of the valve train relative to the crankshaft position (CKP). By monitoring the CMP and the CKP signals, the PCM can accurately time the operation of the fuel injectors. The CMP sensor is connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits that are shared with the CKP sensor

1. The CMP sensor signal circuit
2. A 12-volt reference circuit
3. A low reference circuit

The signal is passed through the ICM to the PCM on the camshaft position signal circuit. The PCM monitors the CMP sensor for errors. If the PCM receives an incorrect number of signals from the CMP sensor, DTC P0341 sets.

This diagnostic procedure supports the following DTC

DTC P0341 Camshaft Position (CMP) Sensor Performance

1. The engine run time is more than 3 seconds.
2. This diagnostic runs continuously when the above condition is met.

1. The PCM detects the following for every two engine revolutions: 36 medium resolution engine speed signals 6 low resolution engine speed signals More than 1 camshaft position signal
2. The condition is met for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. The following conditions may cause this DTC to set: Camshaft reluctor ring damage The sensor coming in contact with the reluctor ring Foreign material passing between the sensor and the reluctor ring Wear or damage to the timing chain or sprickets-Refer to «Timing Chain and Sprockets Cleaning and Inspection (L26)»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) . Excessive camshaft end-play Wiring routed too close to secondary ignition components
2. If you suspect the condition is intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

The numbers below refer to the step numbers on the diagnostic table.

1. 3: This step inspects for electromagnetic interference (EMI) on the CMP sensor circuits.
2. 6: Damage to the face of the sensor could indicate foreign material passing between the CMP sensor and the reluctor wheel. This condition would cause this DTC to set. Damage to the reluctor wheel would affect the CMP sensor output.

DTC P0341

The ignition control module (ICM) controls spark timing when the engine is cranking. During this Bypass mode of operation, the ICM triggers each ignition coil in the proper sequence at a pre-calibrated timing advance. The ICM is connected directly to the powertrain control module (PCM) and includes the following circuits

1. The medium resolution engine speed signal circuit
2. The camshaft position signal circuit
3. A low reference circuit
4. The low resolution engine speed signal circuit
5. The ignition control (IC) timing control circuit
6. The IC timing signal circuit

The PCM sends spark timing signals to the ICM on the IC timing control circuit, but during cranking the ICM grounds these signals. When the PCM begins receiving the 3X reference pulses from the ICM and the engine starts, the PCM applies 5 volts to the IC timing signal circuit allowing the ICM to switch to the IC mode of operation and respond to the spark timing signals from the PCM. The PCM monitors the IC timing control circuit for errors. If the PCM detects a fault, DTC P0350 sets.

This diagnostic procedure supports the following DTC

DTC P0350 Ignition Coil Control Circuit

1. The engine is running or cranking.
2. DTC P0350 runs continuously when the above condition is met.

The PCM detects a fault in the IC timing control circuit for more than 9 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The number below refers to the step number on the diagnostic table.

1. 3: When the low resolution engine speed signal circuit is touched with the test lamp, the PCM detects engine speed and sends timing signals on the IC timing control circuit.

DTC P0350

The crankshaft position (CKP) sensor contains 2 hall-effect switches in one housing. This sensor configuration produces 2 separate CKP sensor pulses. These pulses occur when 2 interrupter rings, mounted to the crankshaft balancer, the outer one containing 18 evenly spaced windows and blades, the inner one containing 3 unevenly spaced windows and blades, pass by the sensors. The 18X sensor produces 18 pulses per engine revolution. The 3X sync sensor produces 3 pulses per engine revolution, each pulse representing a pair of companion cylinders. Both sensors are connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits

1. The CKP sensor 1 signal circuit
2. The CKP sensor 2 signal circuit
3. A shared 12-volt reference circuit
4. A shared low reference circuit

The ICM uses the sensors to determine the engine position and speed. A signal converter within the ICM, using the CKP sensor 1 18X pulse, produces a digital 3X output signal to the powertrain control module (PCM) on the low resolution engine speed signal circuit. The PCM monitors the low resolution engine speed signal circuit for errors. If the PCM does not receive a signal from the ICM, DTC P0385 sets.

This diagnostic procedure supports the following DTC

DTC P0385 Crankshaft Position (CKP) Sensor B Circuit

1. The engine run time is more than 3 seconds.
2. DTC P0385 runs continuously when the above condition is met.

The PCM detects a fault in the low resolution engine speed signal circuit for more than 8 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0385

The crankshaft position (CKP) sensor contains 2 hall-effect switches in one housing. This sensor configuration produces two separate CKP sensor pulses. These pulses occur when two interrupter rings, mounted to the crankshaft balancer, the outer one containing 18 evenly spaced windows and blades, the inner one containing 3 unevenly spaced windows and blades, pass by the sensors. The 18X sensor produces 18 pulses per engine revolution. The 3X sync sensor produces 3 pulses per engine revolution, each pulse representing a pair of companion cylinders. Both sensors are connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits

1. The CKP sensor 1 signal circuit
2. The CKP sensor 2 signal circuit
3. A shared 12-volt reference circuit
4. A shared low reference circuit

The ICM uses the sensors to determine the engine position and speed. A signal converter within the ICM, using the CKP sensor 1 18X pulse, produces a digital 3X output signal to the powertrain control module (PCM) on the low resolution engine speed signal circuit. The PCM monitors the low resolution engine speed signal circuit for errors. If the PCM receives an incorrect number of signals from the ICM, DTC P0386 sets.

This diagnostic procedure supports the following DTC

DTC P0386 Crankshaft Position (CKP) Sensor B Performance

1. The engine run time is more than 3 seconds.
2. DTC P0386 runs continuously when the above condition is met.

1. The PCM detects The following for every 2 engine revolutions: 36 medium resolution engine speed signals 1 CMP sensor signal A number other than 0 or 6 low resolution engine speed signals
2. The condition exists for more than 8 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0386

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module will only allow one EGR flow test during an ignition cycle. To aid in verifying a repair, the control module will allow between 9 and 16 EGR flow test counts during the first ignition cycle following a code clear event.

1. DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0335, P0403, P0404, P0405, P0502, P0503, P0506, P0507, P0604, P0606, P0641, P0651, P1106, P1107, P1125, P2101, P2108, P2135, U0107 are not set.
2. The engine run time may need to be more than 3 minutes.
3. The Ignition 1 Signal parameter is between 11-18 volts.
4. The AC Relay Command parameter does not change.
5. The EGR position is less than 1 percent.
6. The transmission is in third or fourth gear.
7. The Current Gear parameter does not change.
8. The decel fuel cut-off (DFCO) mode is not active.
9. The Intake Air Temperature (IAT) sensor parameter is between 5-100°C (41-212°F).
10. The Engine Coolant Temperature (ECT) sensor parameter is between 75-123°C (167-253°F).
11. The Engine Speed parameter is between 1,000-1,500 RPM.
12. The Manifold Absolute Pressure (MAP) sensor parameter is between 17-43 kPa.
13. The Barometric Pressure (BARO) parameter is more than 74 kPa.
14. The Throttle Position (TP) sensor parameter is less than 1 percent.
15. The Vehicle Speed sensor parameter is between 45-113 km/h (28-70 mph) during deceleration.
16. The vehicle will need to be driven more than 80 km/h (50 mph) and then allowed to decelerate. When the vehicle is decelerating, while meeting all of the criteria listed above, the PCM will enable the EGR flow test to run. As the EGR flow test is running, you will see the desired EGR Position parameter and the EGR Position Sensor parameter on the scan tool momentarily change from 0 to a calibrated value above 0. Additionally, the EGR Flow Test Count parameter on the scan tool will increment when each EGR flow test is completed.

The MAP changes monitored by the PCM during the EGR flow tests indicate an insufficient amount of EGR flow.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Inspect for the following conditions

1. A vacuum restriction to the MAP sensor-A skewed MAP sensor reading can cause the PCM to read incorrect MAP changes during the EGR flow test.
2. An engine that is running poorly due to a mechanical condition such as worn piston rings, worn camshaft, etc.-These types of conditions can cause low engine vacuum and thus can cause a less than expected MAP change during the flow test.
3. Excessive back pressure in the exhaust system may cause this DTC to set. This condition can cause low engine vacuum and thus can cause a less than expected MAP change during the EGR flow test. Possible causes of this could be a restriction in the exhaust system or non original equipment manufacture (OEM) exhaust parts.
4. Exhaust system leaks can cause an insufficient amount of EGR flow through the EGR valve. This condition can cause a less than expected MAP change due to insufficient exhaust back pressure. Possible causes of this could be a leaking exhaust system, a leaking EGR pipe or non OEM exhaust parts.
5. A restriction in the intake manifold such as carbon deposits and casting flash

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Scan Tool Reference

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

Circuit/System Verification

Operate the vehicle within the Conditions for Running the DTC. Observe the EGR Flow Test Count parameter on the scan tool. EGR Flow Test counts may need to be as many as 16 to pass this DTC after the DTCs have been cleared.

1. Test the MAP Sensor for being shifted, stuck, skewed and for correct vacuum supply. Refer to «Manifold Absolute Pressure (MAP) Sensor Diagnosis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
2. Inspect for a vacuum leak between the EGR valve and the intake manifold.
3. Inspect the exhaust system for leaks, restrictions and for modification of OEM parts.
4. Remove the EGR valve and inspect for the following: Cracks Heat distress Pintle for corrosion EGR valve passages for restriction EGR passage in the intake manifold for carbon buildup, casting flash or other restriction If a restriction is identified, refer to «Exhaust Gas Recirculation (EGR) System Cleaning»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__exhaust-gas-recirculation-egr-system-cleaning) . If a condition with the EGR valve is identified, replace the EGR valve.
5. Inspect the engine for correct valve timing and lift or for other conditions that might affect engine vacuum source.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

Repair Verification

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
5. Observe the EGR Flow Test Count parameter on the scan tool. EGR Flow Test counts may need to be as many as 16 to pass this DTC after the DTCs have been cleared.

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

1. The engine is cranking or running.
2. The Ignition 1 Signal parameter is between 11-18 volts.

1. The PCM detects an electrical malfunction in the EGR solenoid high control circuit or the EGR solenoid low control circuit.
2. The above condition is met for more than 20 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

1. Disconnect the EGR valve harness connector and probe the EGR High Control circuit with a test lamp connected to ground. Command the EGR valve from 0 percent to 10 percent and back to 0 percent. The test lamp should illuminate when commanded to 10 percent. If the test lamp remains illuminated when commanded to 0 percent, test the EGR High Control circuit for a short to voltage. If the test lamp does not illuminate, test the EGR High Control circuit for an open, high resistance or short to ground.
2. Connect a test lamp between the EGR High Control circuit and the EGR Low Control Circuit. Command the EGR valve from 0 percent to 10 percent and back to 0 percent. The test lamp should illuminate when commanded to 10 percent. If the test lamp illuminates when commanded to 10 percent replace the EGR valve. If the test lamp does not illuminate, test the EGR Low Control circuit for an open, high resistance. If all circuits test OK, replace the control module.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module is able to determine the difference between the actual EGR position and the desired EGR position when the EGR is commanded open.

1. The Ignition 1 Signal parameter is more than 11 volts.
2. The EGR command will be disabled if the start-up engine coolant temperature (ECT) is less than 5°C (41°F) and will not enable until the ECT is more than 75°C (167°F).
3. The EGR valve is commanded to open.
4. The EGR flow test is not running.

1. The difference between the EGR Position Sensor parameter and the desired EGR Position parameter is more than 15 percent.
2. The above condition is met for more than 20 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

1. With the ignition ON and the engine OFF, observe the DTC information on the scan tool. If DTC P0641 is also set, diagnose those DTCs first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) .
2. Disconnect the EGR harness connector and observe the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 0 percent. If the EGR Position Sensor parameter is more than 0 percent test the EGR Position Sensor signal circuit for a short to voltage or a faulty control module.
3. Using a 3-amp fused jumper wire jumper the EGR 5-volt reference circuit to the EGR Position Sensor Signal circuit at the EGR harness connector and monitor the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 99 percent. If the EGR Position Sensor parameter is less than 99 percent test for an open, high resistance or a short to ground in the EGR Pintle Position Signal circuit.
4. Disconnect the control module and measure the resistance of the EGR High Control circuit and the EGR Low Control circuit. There should be less than 3 ohms of resistance on each circuit. If the resistance is more than 3 ohms, test each circuit for high resistance.

1. If all circuits test OK, replace the EGR Valve.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module is able to determine if the EGR valve position sensor signal voltage is too low.

1. The EGR command will be disabled if the start-up ECT is less than 5°C (41°F) and will not enable until the ECT is more than 75°C (167°F).
2. The EGR flow test is not running.
3. The Ignition 1 Signal parameter is more than 11 volts.

1. The EGR Position Sensor parameter is less than 0.35 volts.
2. The above condition is met for more than 20 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

1. With the ignition ON and the engine OFF, observe the DTC information on the scan tool. If DTC P0641 is also set, diagnose that DTC first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) .
2. Disconnect the EGR harness connector and measure the EGR 5-volt reference circuit for 4.8-5.2 volts. If the voltage is less than 4.8 volts test the EGR valve 5-volt reference circuit for an open, high resistance, a short to ground or a short to the EGR Low Control circuit. If the voltage is more than 5.2 volts test the EGR valve 5-volt reference circuit for a short to voltage or a short to the EGR High Control circuit.
3. Using a 3-amp fused jumper wire connect the EGR valve 5-volt reference circuit to the EGR Position Signal circuit and observe the EGR Position Sensor parameter for more than 4.9 volts. If the EGR Position Sensor parameter is less than 4.9 volts test the EGR Position Signal circuit for an open or high resistance or a short to ground.
4. Using a 3-amp fused jumper wire connect the EGR High Control circuit to the EGR Low Control circuit at the EGR harness connector. Command the EGR Valve to 10 percent while monitoring the EGR Position Sensor parameter. The EGR Position Sensor parameter should remain at 0 percent. If the EGR Position Sensor parameter is more than 0 percent test the EGR Position Signal circuit for a short to the EGR High Control circuit. If all circuits test OK, replace the EGR Valve.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module is able to determine if the EGR valve position sensor signal voltage is too high.

1. DTC P0641 and P0651 are not set.
2. The Ignition 1 Signal parameter is more than 11 volts.
3. The engine is running.
4. The DTC P0401 intrusive test is not active.
5. The EGR valve is not being commanded with a scan tool.
6. The EGR command will be disabled if the start-up ECT is less than 5°C (41°F) and will not enable until the ECT Sensor parameter is more than 75°C (167°F).
7. DTC P0406 runs continuously when the above conditions are met.

The EGR Position Sensor parameter is more than 94.7 percent of the 5-volt reference voltage for longer than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

1. With the ignition ON and the engine OFF, observe the DTC information on the scan tool. If DTC P0641 is also set, diagnose that DTC first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) .
2. Disconnect the EGR harness connector and measure the EGR 5-volt reference circuit for 4.8-5.2 volts. If the voltage is less than 4.8 volts test the EGR valve 5-volt reference circuit for an open, high resistance, a short to ground or a short to the EGR Low Control circuit. If the voltage is more than 5.2 volts test the EGR valve 5-volt reference circuit for a short to voltage or a short to the EGR High Control circuit.
3. Using a 3-amp fused jumper wire connect the EGR 5-volt reference circuit to the EGR Position Signal circuit and observe the EGR Position Sensor parameter for more than 4.9 volts If the EGR Position Sensor parameter is less than 4.9 volts test the EGR Position Signal circuit for an open or high resistance or a short to ground.
4. Using a 3-amp fused jumper wire connect the EGR High Control circuit to the EGR Low Control circuit at the EGR harness connector. Command the EGR valve to 10 percent while monitoring the EGR Position Sensor parameter. The EGR Position Sensor parameter should remain at 0 percent. If the EGR Position Sensor parameter is more than 0 percent test the EGR Position Signal circuit for a short to the EGR High Control circuit. If all circuits test OK, replace the EGR valve.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the secondary AIR injection pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system

1. DTCs P0411 and P2430 run during Phase 1
2. DTCs P2430 and P2440 run during Phase 2
3. DTC P2444 runs during Phase 3

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM can detect faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

DTC P0411 Secondary Air Injection (AIR) System Insufficient Flow diagnostic monitors system airflow. This diagnostic test detects insufficient system flow due to a malfunctioning AIR control solenoid valve/pressure sensor assembly or AIR valve relay; a malfunctioning AIR pump or AIR pump relay; or a restricted or leaking system. When the PCM detects AIR system flow is not sufficient DTC P0411 sets. DTC P0411 runs during Phase 1.

1. The AIR system flow is sufficient and DTC P0411 passes. DTC P0411 AIR diagnostic proceeds to Phase 2.
2. The AIR system flow is not sufficient. DTC P0411 AIR diagnostic fails, testing is stopped and DTC P0411 sets.

This diagnostic procedure supports the following DTC

DTC P0411 Secondary Air Injection (AIR) System Insufficient Flow

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0201-P0206, P0300, P0350, P0412, P0418, P0420, P0606, P0641, P0651, P1350, P2430, P2431, P2432, P2433 are not set.
2. The system voltage is between 10-18 volts.
3. The engine is running.
4. The start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F)
5. The start-up intake air temperature (IAT) is between 5-60°C (41-140°F)
6. The BARO parameter is more than 60 kPa.
7. The MAF sensor parameter is between 3-24 g/s.
8. DTC P0411 runs once per trip start up when the above conditions are met and AIR pump operation is requested.

1. The AIR system does not meet expected flow conditions during AIR pump Phase 1 operation.
2. DTC P0411 sets with in 22 seconds when the above conditions are met.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. An intermittent may be caused by any of the following conditions: Low system airflow Excessive exhaust system back-pressure Pinched, restricted, split or damaged pipes/hoses Restrictions in the AIR pump inlet hose Pitted contacts in the AIR pump relay, AIR valve relay-Tap on the AIR pump relay or AIR valve relay to attempt to duplicate an intermittent condition. Yellow tinted water in the AIR pump may indicate a control/shut-off valve failure. Water or debris ingested into the AIR pump Observe the Freeze Frame/Failure Records to aid in conditions of setting DTC P0411.
2. Thoroughly inspect any circuits that are suspected of causing the intermittent condition. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

The numbers below refer to the step numbers on the diagnostic table.

1. 9: This step determines if excessive resistance on the supply voltage circuit between the AIR pump fuse and the AIR pump relay is the cause for an inoperative AIR pump. One ohm of resistance on this circuit can prevent the AIR pump from running.
2. 13: This step determines if excessive resistance on the AIR pump relay circuit and PCM driver is the cause for an inoperative AIR pump relay. The test lamp in series is intended to generate a electrical load on this circuit. Fifty ohms of resistance on this circuit can prevent the AIR pump relay from operating.
3. 17: This step determines if excessive resistance on the supply circuit is the cause for an inoperative AIR pump. One ohm of resistance on this circuit can prevent the AIR pump from running.
4. 18: This step determines if excessive resistance on the ground circuit is the cause for an inoperative AIR pump. One ohm of resistance on this circuit can prevent the AIR pump from running.
5. 27: This step commands both the AIR pump and AIR valve relays ON.
6. 60: This step determines if the AIR system is operating normally. When the AIR valve relay is commanded ON the AIR pump should run with the AIR control/shut-off valve OPEN.

DTC P0411 (L26, NU3)

The secondary air injection (AIR) valve relay controls high current to the AIR control solenoid valve/pressure sensor assembly. The AIR valve relay armature is held in the open position by spring tension. Ignition voltage is supplied to the AIR valve relay coil and armature when the key is in the ON position. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). One of the ODM output circuits is configured to operate as a low side driver for the AIR valve relay. The low side driver also incorporates a fault detection circuit, which is continuously monitored by the PCM. If the PCM detects a low side circuit fault, the driver will be turned OFF for the rest of the trip. The voltage on the control circuit should be battery voltage when the key is ON and the AIR valve relay is at rest. If the fault detection circuit measures a low voltage under this condition, then an open or a short to ground on the control circuit or the ignition 1 voltage circuit or an AIR valve relay coil fault may be present. If the PCM detects a low voltage on the control circuit when the AIR valve relay is commanded OFF, DTC P0412 will set.

This diagnostic procedure supports the following DTC

DTC P0412 Secondary Air Injection (AIR) Solenoid Relay Control Circuit

1. The ignition switch is in the Crank or Run position.
2. The system voltage is between 9-18 volts.
3. This DTC runs on a 100 ms loop.
4. DTC P0412 runs continuously when the above conditions are met.

The condition exists for at least 2 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 7: This step verifies that the PCM is providing ground to the AIR valve relay when the command is ON. Listen for a click when the relay operates. Be sure to command the AIR valve relay ON and the OFF. Repeat the commands as necessary.
2. 8: This step tests if a ground is constantly being applied to the AIR valve relay.
3. 9: This step tests for a short to voltage on the AIR valve relay control circuit. This will allow the AIR solenoid to hold the shut-off valve open continuously with the key in the OFF position.
4. 10: This step tests for a short to ground on the AIR valve relay control circuit. This will allow the AIR valve to hold the shut-off valve open continuously with the key in the ON position.

DTC P0412 (L26, NU3)

The secondary air injection (AIR) pump relay controls high current to the AIR pump. The AIR pump relay armature is held in the open position by spring tension. Ignition voltage is supplied to the AIR pump relay coil when the ignition is ON. Battery positive voltage is supplied to the armature contacts at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). One of the ODM output circuits is configured to operate as a low side driver for the AIR pump relay. The low side driver also incorporates a fault detection circuit that is continuously monitored by the PCM. If the PCM detects a low side driver circuit fault, the driver will be turned OFF for the rest of the trip. The voltage on the control circuit should be battery voltage when the ignition is ON and the AIR pump relay is at rest. If the fault detection circuit measures a low voltage under this condition, then an open, a short to ground on the control or the ignition 1 circuits or an open AIR pump relay coil fault may be present. If the PCM detects low voltage on the AIR pump relay control circuit when the AIR pump relay is commanded OFF, DTC P0418 will set.

This diagnostic procedure supports the following DTC

DTC P0418 Secondary Air Injection (AIR) Pump Control Circuit

1. The ignition switch is in the Crank or Run position.
2. The system voltage is between 9-18 volts.
3. This DTC runs on a 100 ms loop.
4. DTC P0418 runs continuously once the above conditions are met.

1. The PCM detects a low voltage on the AIR pump relay control circuit with the key ON and the AIR pump relay commanded OFF.
2. The condition exists for at least 2 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 7: This step verifies that the PCM is providing ground to the AIR pump relay when the command is ON.
2. 8: This step tests if a ground is constantly being applied to the AIR pump relay control circuit.
3. 9: This step tests for a short to voltage on the AIR pump relay control circuit. This will allow the AIR pump to run continually with the key in the OFF position. If the pump runs continually, the pump will fail.
4. 10: This step tests for a short to ground on the AIR pump relay control circuit. This will allow the AIR pump to operate continually with the key in the ON position. If the pump runs continually, the pump will fail.

DTC P0418 (L26, NU3)

A three-way catalytic (TWC) converter controls emissions of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction which oxidizes the HC and the CO that are present in the exhaust gas. This process converts the HC and the CO into water vapor and carbon dioxide (CO2) and reduces the NOx, converting the NOx into nitrogen. The catalytic converter also stores oxygen. The powertrain control module (PCM) monitors this process by using a heated oxygen sensor (HO2S) that is in the exhaust stream after the TWC. This HO2S 2, also referred to as the catalyst monitor sensor, produces an output signal that the PCM uses to calculate the oxygen storage capacity of the catalyst. This indicates the ability of the catalyst to convert the exhaust emissions efficiently. The PCM monitors the efficiency of the catalyst by allowing the catalyst to heat, then wait for a stabilization period while the engine is idling. The PCM then adds and removes fuel while monitoring the HO2S 2. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the response of the HO2S 1, which is located before the TWC. When the HO2S 2 response is near that of the HO2S 1, the oxygen storage capability and efficiency of the catalyst may be degraded below an acceptable threshold. If the PCM detects the degraded condition, DTC P0420 sets.

This diagnostic procedure supports the following DTC

DTC P0420 Catalyst System Low Efficiency Bank 1

1. DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 where applicable, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0325, P0327, P0332, P0335, P0336, P0340, P0341, P0401, P0403, P0404, P0405, P0406, P0442, P0443, P0446, P0449, P0455, P0496, P0506, P0507, P1133, P1134, P1258, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138, P2A00, P2A01, U0107 are not set.
2. The engine has been running for more than 10 minutes.
3. The engine speed is within 200 RPM of the desired idle.
4. The engine coolant temperature (ECT) is between 75-126°C (167-259°F).
5. The barometric pressure (BARO) is more than 74 kPa.
6. The vehicle is in Closed Loop.
7. The intake air temperature (IAT) is between -7 and +100°C (+19 and +212°F).
8. The battery voltage is more than 10.7 volts.
9. The throttle position (TP) is 1.5 percent or less.
10. The short term fuel trim (FT) is between -10 and +10 percent.
11. The engine load must be stable.
12. Warm the catalyst by performing the following procedures: Fully open the hood. Place the transaxle in PARK for automatic transaxle. Place the transaxle is NEUTRAL for manual transaxle, with clutch pedal depressed. Set the parking brake. Press and hold the service brake.
13. This diagnostic attempts one test during each valid idle period once the above conditions have been met for 5 seconds. This diagnostic attempts up to 6 tests during each drive cycle. The first test may be run after the initial warm-up period of 10 minutes. Maintain engine speed between 2,000-3,000 RPM in park or neutral for 2 minutes. Allow the engine to return to a stabilized idle. Shift into drive for an automatic transmission, without touching the accelerator in order for the test to run. Between each subsequent test, maintain engine speed between 2,000-3,000 RPM in park or neutral for 2 minutes. Allow the engine to return to a stabilized idle. Shift into drive for an automatic transmission, without touching the accelerator in order for the test to run.
14. Test the catalyst by performing the following procedures: Idle the engine and place the vehicle in Drive or depress the clutch pedal for a manual transmission vehicle, to activate the diagnostic. Within 60 seconds, the air fuel ratio will transition lean, below 14.1, for up to 7 seconds and then may transition rich, above 15.3, for up to 7 seconds. Verify if DTC P0420 has passed or failed this ignition cycle with the scan tool.

The PCM determines that the efficiency of the catalyst has degraded below a calibrated threshold. This diagnostic may conclude in as few as one test attempt. However, this diagnostic may require as many as 18 test attempts, which would require at least 3 drive cycles. Each test attempt concludes within 2 minutes.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. These conditions may cause a catalytic converter to degrade. Inspect for the following conditions: An engine misfire High engine oil or high coolant consumption Retarded spark timing A weak or poor spark A lean fuel mixture A rich fuel mixture A damaged oxygen sensor or wiring harness The catalyst test may abort if the vehicle falls outside the conditions for running the DTC. The catalyst test may abort due to a change in engine load such as the A/C or engine cooling fan cycling. If 18 tests have been attempted and the DTC has not run or passed during this key cycle, turn the key to OFF for 30 seconds. Perform the conditions for running a second time.
2. If an intermittent condition cannot be duplicated, the information included in the Freeze Frame/Failure Records can be useful in determining the vehicle operating conditions when the DTC was set.
3. The catalyst may have been temporarily contaminated with a chemical from a fuel additive, fuel contamination or any of the above conditions.
4. If the condition is determined to be intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

DTC P0420

This DTC tests the evaporative emission (EVAP) system for a small leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge solenoid valve ON and the EVAP canister vent solenoid valve ON. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time or vacuum level, the control module turns the EVAP canister purge solenoid valve OFF, sealing the system and monitors the FTP sensor input in order to determine the EVAP system vacuum decay. If the control module detects a leak larger than a calibrated amount, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

DTC P0442

This diagnostic procedure supports the following DTC

DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected

1. Before the powertrain control module (PCM) can report that DTC P0442 failed, DTCs P0446, P0455 and P0496 must run and pass.
2. DTCs P0111, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0443, P0449, P0452, P0453, P0462, P0463, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1120, P1121, P1122 are not set.
3. The ignition voltage is between 10-18 volts.
4. The barometric pressure (BARO) is more than 75 kPa.
5. The fuel level is between 15-85 percent.
6. The engine coolant temperature (ECT) is between 4-39°C (39-86°F).
7. The intake air temperature (IAT) is between 4-30°C (39-86°F).
8. The start up ECT and IAT are within 9°C (16°F) of each other.
9. The vehicle speed sensor (VSS) is less than 129 km/h (80 mph).
10. The vehicle must be driven more than 8.4 kilometers (5.2 miles).
11. DTC P0442 runs once per cold start when the above conditions are met.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light.
2. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
3. For intermittent conditions, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

The numbers below refer to the step numbers on the diagnostic table.

1. 3: Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. 5: This step verifies that repairs are complete.

DTC P0442

An ignition voltage is supplied directly to the evaporative emission (EVAP) canister purge solenoid valve. The EVAP canister purge solenoid valve is pulse width modulated (PWM). The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. The control module controls the EVAP canister purge solenoid valve ON time by grounding the control circuit via an internal switch called a driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit

1. The ignition is in the Crank or Run position.
2. The system voltage is between 11-18 volts.

1. The control module detects that the commanded state of the driver and the actual state of the control circuit DO NOT match.
2. The above condition is present for a minimum of 2 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0443

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

DTC P0446

This diagnostic procedure supports the following DTC

DTC P0446 Evaporative Emission Vent System Performance

1. Before the powertrain control module (PCM) can report that DTC P0446 failed, DTCs P0442 and P0496 must run and pass.
2. DTC P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0128, P0443, P0449, P0452, P0453, P0455, P0502, P1106, P1107, P1111, P1112, P1114, P1115 are not set.
3. The ignition voltage is between 10-18 volts.
4. The barometric pressure (BARO) is more than 75 kPa.
5. The fuel level is between 15-85 percent.
6. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
7. The intake air temperature (IAT) is between 4-30°C (39-86°F).
8. The start up ECT and IAT are within 9°C (16°F) of each other.
9. The vehicle speed sensor (VSS) is less than 129 km/h (80 mph).
10. DTC P0446 runs once per cold start when the above conditions are met.

The fuel tank pressure is more than -10 inches H2O.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. When using the Evaporative Emission System Tester (EEST) to apply pressure, you can regulate the amount of pressure by activating the remote switch on and off while observing pressure in the EVAP system using a scan tool. DO NOT use more than 5 inches H2O. More than 5 inches H2O applied to the EVAP system can cause the canister vent solenoid valve to temporarily remain in the closed position, which could lead to misdiagnosis in this procedure.
2. An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
3. For intermittent conditions, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

The number below refers to the step number on the diagnostic table.

1. 3: This test determines if the failure is present or intermittent.

DTC P0446

An ignition voltage is supplied to the evaporative emission (EVAP) canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the solenoid by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the OPEN or CLOSED states of the EVAP canister vent solenoid valve.

DTC P0449

This diagnostic procedure supports the following DTC

DTC P0449 Evaporative Emission Vent Solenoid Control Circuit

1. The ignition is in the Crank or Run position.
2. The system voltage is between 11-18 volts.

1. The control module detects that the commanded state of the driver and the actual state of the control circuit do NOT match.
2. The above condition is present for a minimum of 2 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0449

See also:
• Engine Controls Schematics
• Powertrain Control Module (PCM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Diagnostic Trouble Code (DTC) List - Vehicle
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Control Module References
• Symptoms - Hydraulic Brakes
• Symptoms - Engine Mechanical
• Crankcase Ventilation System Inspection/Diagnosis
• Exhaust Gas Recirculation (EGR) System Cleaning
• Restricted Exhaust
• Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool)
• Spark Plug Wire Inspection
• Ignition System Specifications
• Spark Plug Inspection
• CKP System Variation Learn Procedure
• Diagnostic Repair Verification
• Probing Electrical Connectors
• Scan Tool Data List
• Scan Tool Output Controls
• Engine Control Module Programming and Setup
• Measuring Voltage Drop
• Using Connector Test Adapters
• Road Test Caution
• Three-Way Catalytic Converter Damage Notice
• Exhaust Leakage
• Lifting and Jacking the Vehicle
• Special Tools
• DTC P0420